1 /*
2 * linux/fs/fcntl.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7 #include <linux/syscalls.h>
8 #include <linux/init.h>
9 #include <linux/mm.h>
10 #include <linux/fs.h>
11 #include <linux/file.h>
12 #include <linux/fdtable.h>
13 #include <linux/capability.h>
14 #include <linux/dnotify.h>
15 #include <linux/slab.h>
16 #include <linux/module.h>
17 #include <linux/pipe_fs_i.h>
18 #include <linux/security.h>
19 #include <linux/ptrace.h>
20 #include <linux/signal.h>
21 #include <linux/rcupdate.h>
22 #include <linux/pid_namespace.h>
23 #include <linux/user_namespace.h>
24 #include <linux/shmem_fs.h>
25
26 #include <asm/poll.h>
27 #include <asm/siginfo.h>
28 #include <asm/uaccess.h>
29
30 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
31
setfl(int fd,struct file * filp,unsigned long arg)32 static int setfl(int fd, struct file * filp, unsigned long arg)
33 {
34 struct inode * inode = file_inode(filp);
35 int error = 0;
36
37 /*
38 * O_APPEND cannot be cleared if the file is marked as append-only
39 * and the file is open for write.
40 */
41 if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
42 return -EPERM;
43
44 /* O_NOATIME can only be set by the owner or superuser */
45 if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
46 if (!inode_owner_or_capable(inode))
47 return -EPERM;
48
49 /* required for strict SunOS emulation */
50 if (O_NONBLOCK != O_NDELAY)
51 if (arg & O_NDELAY)
52 arg |= O_NONBLOCK;
53
54 if (arg & O_DIRECT) {
55 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
56 !filp->f_mapping->a_ops->direct_IO)
57 return -EINVAL;
58 }
59
60 if (filp->f_op->check_flags)
61 error = filp->f_op->check_flags(arg);
62 if (error)
63 return error;
64
65 /*
66 * ->fasync() is responsible for setting the FASYNC bit.
67 */
68 if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op->fasync) {
69 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
70 if (error < 0)
71 goto out;
72 if (error > 0)
73 error = 0;
74 }
75 spin_lock(&filp->f_lock);
76 filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
77 spin_unlock(&filp->f_lock);
78
79 out:
80 return error;
81 }
82
f_modown(struct file * filp,struct pid * pid,enum pid_type type,int force)83 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
84 int force)
85 {
86 write_lock_irq(&filp->f_owner.lock);
87 if (force || !filp->f_owner.pid) {
88 put_pid(filp->f_owner.pid);
89 filp->f_owner.pid = get_pid(pid);
90 filp->f_owner.pid_type = type;
91
92 if (pid) {
93 const struct cred *cred = current_cred();
94 filp->f_owner.uid = cred->uid;
95 filp->f_owner.euid = cred->euid;
96 }
97 }
98 write_unlock_irq(&filp->f_owner.lock);
99 }
100
__f_setown(struct file * filp,struct pid * pid,enum pid_type type,int force)101 void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
102 int force)
103 {
104 security_file_set_fowner(filp);
105 f_modown(filp, pid, type, force);
106 }
107 EXPORT_SYMBOL(__f_setown);
108
f_setown(struct file * filp,unsigned long arg,int force)109 void f_setown(struct file *filp, unsigned long arg, int force)
110 {
111 enum pid_type type;
112 struct pid *pid;
113 int who = arg;
114 type = PIDTYPE_PID;
115 if (who < 0) {
116 /* avoid overflow below */
117 if (who == INT_MIN)
118 return;
119
120 type = PIDTYPE_PGID;
121 who = -who;
122 }
123 rcu_read_lock();
124 pid = find_vpid(who);
125 __f_setown(filp, pid, type, force);
126 rcu_read_unlock();
127 }
128 EXPORT_SYMBOL(f_setown);
129
f_delown(struct file * filp)130 void f_delown(struct file *filp)
131 {
132 f_modown(filp, NULL, PIDTYPE_PID, 1);
133 }
134
f_getown(struct file * filp)135 pid_t f_getown(struct file *filp)
136 {
137 pid_t pid;
138 read_lock(&filp->f_owner.lock);
139 pid = pid_vnr(filp->f_owner.pid);
140 if (filp->f_owner.pid_type == PIDTYPE_PGID)
141 pid = -pid;
142 read_unlock(&filp->f_owner.lock);
143 return pid;
144 }
145
f_setown_ex(struct file * filp,unsigned long arg)146 static int f_setown_ex(struct file *filp, unsigned long arg)
147 {
148 struct f_owner_ex __user *owner_p = (void __user *)arg;
149 struct f_owner_ex owner;
150 struct pid *pid;
151 int type;
152 int ret;
153
154 ret = copy_from_user(&owner, owner_p, sizeof(owner));
155 if (ret)
156 return -EFAULT;
157
158 switch (owner.type) {
159 case F_OWNER_TID:
160 type = PIDTYPE_MAX;
161 break;
162
163 case F_OWNER_PID:
164 type = PIDTYPE_PID;
165 break;
166
167 case F_OWNER_PGRP:
168 type = PIDTYPE_PGID;
169 break;
170
171 default:
172 return -EINVAL;
173 }
174
175 rcu_read_lock();
176 pid = find_vpid(owner.pid);
177 if (owner.pid && !pid)
178 ret = -ESRCH;
179 else
180 __f_setown(filp, pid, type, 1);
181 rcu_read_unlock();
182
183 return ret;
184 }
185
f_getown_ex(struct file * filp,unsigned long arg)186 static int f_getown_ex(struct file *filp, unsigned long arg)
187 {
188 struct f_owner_ex __user *owner_p = (void __user *)arg;
189 struct f_owner_ex owner;
190 int ret = 0;
191
192 read_lock(&filp->f_owner.lock);
193 owner.pid = pid_vnr(filp->f_owner.pid);
194 switch (filp->f_owner.pid_type) {
195 case PIDTYPE_MAX:
196 owner.type = F_OWNER_TID;
197 break;
198
199 case PIDTYPE_PID:
200 owner.type = F_OWNER_PID;
201 break;
202
203 case PIDTYPE_PGID:
204 owner.type = F_OWNER_PGRP;
205 break;
206
207 default:
208 WARN_ON(1);
209 ret = -EINVAL;
210 break;
211 }
212 read_unlock(&filp->f_owner.lock);
213
214 if (!ret) {
215 ret = copy_to_user(owner_p, &owner, sizeof(owner));
216 if (ret)
217 ret = -EFAULT;
218 }
219 return ret;
220 }
221
222 #ifdef CONFIG_CHECKPOINT_RESTORE
f_getowner_uids(struct file * filp,unsigned long arg)223 static int f_getowner_uids(struct file *filp, unsigned long arg)
224 {
225 struct user_namespace *user_ns = current_user_ns();
226 uid_t __user *dst = (void __user *)arg;
227 uid_t src[2];
228 int err;
229
230 read_lock(&filp->f_owner.lock);
231 src[0] = from_kuid(user_ns, filp->f_owner.uid);
232 src[1] = from_kuid(user_ns, filp->f_owner.euid);
233 read_unlock(&filp->f_owner.lock);
234
235 err = put_user(src[0], &dst[0]);
236 err |= put_user(src[1], &dst[1]);
237
238 return err;
239 }
240 #else
f_getowner_uids(struct file * filp,unsigned long arg)241 static int f_getowner_uids(struct file *filp, unsigned long arg)
242 {
243 return -EINVAL;
244 }
245 #endif
246
do_fcntl(int fd,unsigned int cmd,unsigned long arg,struct file * filp)247 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
248 struct file *filp)
249 {
250 long err = -EINVAL;
251
252 switch (cmd) {
253 case F_DUPFD:
254 err = f_dupfd(arg, filp, 0);
255 break;
256 case F_DUPFD_CLOEXEC:
257 err = f_dupfd(arg, filp, O_CLOEXEC);
258 break;
259 case F_GETFD:
260 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
261 break;
262 case F_SETFD:
263 err = 0;
264 set_close_on_exec(fd, arg & FD_CLOEXEC);
265 break;
266 case F_GETFL:
267 err = filp->f_flags;
268 break;
269 case F_SETFL:
270 err = setfl(fd, filp, arg);
271 break;
272 #if BITS_PER_LONG != 32
273 /* 32-bit arches must use fcntl64() */
274 case F_OFD_GETLK:
275 #endif
276 case F_GETLK:
277 err = fcntl_getlk(filp, cmd, (struct flock __user *) arg);
278 break;
279 #if BITS_PER_LONG != 32
280 /* 32-bit arches must use fcntl64() */
281 case F_OFD_SETLK:
282 case F_OFD_SETLKW:
283 #endif
284 /* Fallthrough */
285 case F_SETLK:
286 case F_SETLKW:
287 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
288 break;
289 case F_GETOWN:
290 /*
291 * XXX If f_owner is a process group, the
292 * negative return value will get converted
293 * into an error. Oops. If we keep the
294 * current syscall conventions, the only way
295 * to fix this will be in libc.
296 */
297 err = f_getown(filp);
298 force_successful_syscall_return();
299 break;
300 case F_SETOWN:
301 f_setown(filp, arg, 1);
302 err = 0;
303 break;
304 case F_GETOWN_EX:
305 err = f_getown_ex(filp, arg);
306 break;
307 case F_SETOWN_EX:
308 err = f_setown_ex(filp, arg);
309 break;
310 case F_GETOWNER_UIDS:
311 err = f_getowner_uids(filp, arg);
312 break;
313 case F_GETSIG:
314 err = filp->f_owner.signum;
315 break;
316 case F_SETSIG:
317 /* arg == 0 restores default behaviour. */
318 if (!valid_signal(arg)) {
319 break;
320 }
321 err = 0;
322 filp->f_owner.signum = arg;
323 break;
324 case F_GETLEASE:
325 err = fcntl_getlease(filp);
326 break;
327 case F_SETLEASE:
328 err = fcntl_setlease(fd, filp, arg);
329 break;
330 case F_NOTIFY:
331 err = fcntl_dirnotify(fd, filp, arg);
332 break;
333 case F_SETPIPE_SZ:
334 case F_GETPIPE_SZ:
335 err = pipe_fcntl(filp, cmd, arg);
336 break;
337 case F_ADD_SEALS:
338 case F_GET_SEALS:
339 err = shmem_fcntl(filp, cmd, arg);
340 break;
341 default:
342 break;
343 }
344 return err;
345 }
346
check_fcntl_cmd(unsigned cmd)347 static int check_fcntl_cmd(unsigned cmd)
348 {
349 switch (cmd) {
350 case F_DUPFD:
351 case F_DUPFD_CLOEXEC:
352 case F_GETFD:
353 case F_SETFD:
354 case F_GETFL:
355 return 1;
356 }
357 return 0;
358 }
359
SYSCALL_DEFINE3(fcntl,unsigned int,fd,unsigned int,cmd,unsigned long,arg)360 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
361 {
362 struct fd f = fdget_raw(fd);
363 long err = -EBADF;
364
365 if (!f.file)
366 goto out;
367
368 if (unlikely(f.file->f_mode & FMODE_PATH)) {
369 if (!check_fcntl_cmd(cmd))
370 goto out1;
371 }
372
373 err = security_file_fcntl(f.file, cmd, arg);
374 if (!err)
375 err = do_fcntl(fd, cmd, arg, f.file);
376
377 out1:
378 fdput(f);
379 out:
380 return err;
381 }
382
383 #if BITS_PER_LONG == 32
SYSCALL_DEFINE3(fcntl64,unsigned int,fd,unsigned int,cmd,unsigned long,arg)384 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
385 unsigned long, arg)
386 {
387 struct fd f = fdget_raw(fd);
388 long err = -EBADF;
389
390 if (!f.file)
391 goto out;
392
393 if (unlikely(f.file->f_mode & FMODE_PATH)) {
394 if (!check_fcntl_cmd(cmd))
395 goto out1;
396 }
397
398 err = security_file_fcntl(f.file, cmd, arg);
399 if (err)
400 goto out1;
401
402 switch (cmd) {
403 case F_GETLK64:
404 case F_OFD_GETLK:
405 err = fcntl_getlk64(f.file, cmd, (struct flock64 __user *) arg);
406 break;
407 case F_SETLK64:
408 case F_SETLKW64:
409 case F_OFD_SETLK:
410 case F_OFD_SETLKW:
411 err = fcntl_setlk64(fd, f.file, cmd,
412 (struct flock64 __user *) arg);
413 break;
414 default:
415 err = do_fcntl(fd, cmd, arg, f.file);
416 break;
417 }
418 out1:
419 fdput(f);
420 out:
421 return err;
422 }
423 #endif
424
425 /* Table to convert sigio signal codes into poll band bitmaps */
426
427 static const long band_table[NSIGPOLL] = {
428 POLLIN | POLLRDNORM, /* POLL_IN */
429 POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */
430 POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */
431 POLLERR, /* POLL_ERR */
432 POLLPRI | POLLRDBAND, /* POLL_PRI */
433 POLLHUP | POLLERR /* POLL_HUP */
434 };
435
sigio_perm(struct task_struct * p,struct fown_struct * fown,int sig)436 static inline int sigio_perm(struct task_struct *p,
437 struct fown_struct *fown, int sig)
438 {
439 const struct cred *cred;
440 int ret;
441
442 rcu_read_lock();
443 cred = __task_cred(p);
444 ret = ((uid_eq(fown->euid, GLOBAL_ROOT_UID) ||
445 uid_eq(fown->euid, cred->suid) || uid_eq(fown->euid, cred->uid) ||
446 uid_eq(fown->uid, cred->suid) || uid_eq(fown->uid, cred->uid)) &&
447 !security_file_send_sigiotask(p, fown, sig));
448 rcu_read_unlock();
449 return ret;
450 }
451
send_sigio_to_task(struct task_struct * p,struct fown_struct * fown,int fd,int reason,int group)452 static void send_sigio_to_task(struct task_struct *p,
453 struct fown_struct *fown,
454 int fd, int reason, int group)
455 {
456 /*
457 * F_SETSIG can change ->signum lockless in parallel, make
458 * sure we read it once and use the same value throughout.
459 */
460 int signum = ACCESS_ONCE(fown->signum);
461
462 if (!sigio_perm(p, fown, signum))
463 return;
464
465 switch (signum) {
466 siginfo_t si;
467 default:
468 /* Queue a rt signal with the appropriate fd as its
469 value. We use SI_SIGIO as the source, not
470 SI_KERNEL, since kernel signals always get
471 delivered even if we can't queue. Failure to
472 queue in this case _should_ be reported; we fall
473 back to SIGIO in that case. --sct */
474 si.si_signo = signum;
475 si.si_errno = 0;
476 si.si_code = reason;
477 /* Make sure we are called with one of the POLL_*
478 reasons, otherwise we could leak kernel stack into
479 userspace. */
480 BUG_ON((reason & __SI_MASK) != __SI_POLL);
481 if (reason - POLL_IN >= NSIGPOLL)
482 si.si_band = ~0L;
483 else
484 si.si_band = band_table[reason - POLL_IN];
485 si.si_fd = fd;
486 if (!do_send_sig_info(signum, &si, p, group))
487 break;
488 /* fall-through: fall back on the old plain SIGIO signal */
489 case 0:
490 do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
491 }
492 }
493
send_sigio(struct fown_struct * fown,int fd,int band)494 void send_sigio(struct fown_struct *fown, int fd, int band)
495 {
496 struct task_struct *p;
497 enum pid_type type;
498 struct pid *pid;
499 int group = 1;
500
501 read_lock(&fown->lock);
502
503 type = fown->pid_type;
504 if (type == PIDTYPE_MAX) {
505 group = 0;
506 type = PIDTYPE_PID;
507 }
508
509 pid = fown->pid;
510 if (!pid)
511 goto out_unlock_fown;
512
513 read_lock(&tasklist_lock);
514 do_each_pid_task(pid, type, p) {
515 send_sigio_to_task(p, fown, fd, band, group);
516 } while_each_pid_task(pid, type, p);
517 read_unlock(&tasklist_lock);
518 out_unlock_fown:
519 read_unlock(&fown->lock);
520 }
521
send_sigurg_to_task(struct task_struct * p,struct fown_struct * fown,int group)522 static void send_sigurg_to_task(struct task_struct *p,
523 struct fown_struct *fown, int group)
524 {
525 if (sigio_perm(p, fown, SIGURG))
526 do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
527 }
528
send_sigurg(struct fown_struct * fown)529 int send_sigurg(struct fown_struct *fown)
530 {
531 struct task_struct *p;
532 enum pid_type type;
533 struct pid *pid;
534 int group = 1;
535 int ret = 0;
536
537 read_lock(&fown->lock);
538
539 type = fown->pid_type;
540 if (type == PIDTYPE_MAX) {
541 group = 0;
542 type = PIDTYPE_PID;
543 }
544
545 pid = fown->pid;
546 if (!pid)
547 goto out_unlock_fown;
548
549 ret = 1;
550
551 read_lock(&tasklist_lock);
552 do_each_pid_task(pid, type, p) {
553 send_sigurg_to_task(p, fown, group);
554 } while_each_pid_task(pid, type, p);
555 read_unlock(&tasklist_lock);
556 out_unlock_fown:
557 read_unlock(&fown->lock);
558 return ret;
559 }
560
561 static DEFINE_SPINLOCK(fasync_lock);
562 static struct kmem_cache *fasync_cache __read_mostly;
563
fasync_free_rcu(struct rcu_head * head)564 static void fasync_free_rcu(struct rcu_head *head)
565 {
566 kmem_cache_free(fasync_cache,
567 container_of(head, struct fasync_struct, fa_rcu));
568 }
569
570 /*
571 * Remove a fasync entry. If successfully removed, return
572 * positive and clear the FASYNC flag. If no entry exists,
573 * do nothing and return 0.
574 *
575 * NOTE! It is very important that the FASYNC flag always
576 * match the state "is the filp on a fasync list".
577 *
578 */
fasync_remove_entry(struct file * filp,struct fasync_struct ** fapp)579 int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
580 {
581 struct fasync_struct *fa, **fp;
582 int result = 0;
583
584 spin_lock(&filp->f_lock);
585 spin_lock(&fasync_lock);
586 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
587 if (fa->fa_file != filp)
588 continue;
589
590 spin_lock_irq(&fa->fa_lock);
591 fa->fa_file = NULL;
592 spin_unlock_irq(&fa->fa_lock);
593
594 *fp = fa->fa_next;
595 call_rcu(&fa->fa_rcu, fasync_free_rcu);
596 filp->f_flags &= ~FASYNC;
597 result = 1;
598 break;
599 }
600 spin_unlock(&fasync_lock);
601 spin_unlock(&filp->f_lock);
602 return result;
603 }
604
fasync_alloc(void)605 struct fasync_struct *fasync_alloc(void)
606 {
607 return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
608 }
609
610 /*
611 * NOTE! This can be used only for unused fasync entries:
612 * entries that actually got inserted on the fasync list
613 * need to be released by rcu - see fasync_remove_entry.
614 */
fasync_free(struct fasync_struct * new)615 void fasync_free(struct fasync_struct *new)
616 {
617 kmem_cache_free(fasync_cache, new);
618 }
619
620 /*
621 * Insert a new entry into the fasync list. Return the pointer to the
622 * old one if we didn't use the new one.
623 *
624 * NOTE! It is very important that the FASYNC flag always
625 * match the state "is the filp on a fasync list".
626 */
fasync_insert_entry(int fd,struct file * filp,struct fasync_struct ** fapp,struct fasync_struct * new)627 struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
628 {
629 struct fasync_struct *fa, **fp;
630
631 spin_lock(&filp->f_lock);
632 spin_lock(&fasync_lock);
633 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
634 if (fa->fa_file != filp)
635 continue;
636
637 spin_lock_irq(&fa->fa_lock);
638 fa->fa_fd = fd;
639 spin_unlock_irq(&fa->fa_lock);
640 goto out;
641 }
642
643 spin_lock_init(&new->fa_lock);
644 new->magic = FASYNC_MAGIC;
645 new->fa_file = filp;
646 new->fa_fd = fd;
647 new->fa_next = *fapp;
648 rcu_assign_pointer(*fapp, new);
649 filp->f_flags |= FASYNC;
650
651 out:
652 spin_unlock(&fasync_lock);
653 spin_unlock(&filp->f_lock);
654 return fa;
655 }
656
657 /*
658 * Add a fasync entry. Return negative on error, positive if
659 * added, and zero if did nothing but change an existing one.
660 */
fasync_add_entry(int fd,struct file * filp,struct fasync_struct ** fapp)661 static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
662 {
663 struct fasync_struct *new;
664
665 new = fasync_alloc();
666 if (!new)
667 return -ENOMEM;
668
669 /*
670 * fasync_insert_entry() returns the old (update) entry if
671 * it existed.
672 *
673 * So free the (unused) new entry and return 0 to let the
674 * caller know that we didn't add any new fasync entries.
675 */
676 if (fasync_insert_entry(fd, filp, fapp, new)) {
677 fasync_free(new);
678 return 0;
679 }
680
681 return 1;
682 }
683
684 /*
685 * fasync_helper() is used by almost all character device drivers
686 * to set up the fasync queue, and for regular files by the file
687 * lease code. It returns negative on error, 0 if it did no changes
688 * and positive if it added/deleted the entry.
689 */
fasync_helper(int fd,struct file * filp,int on,struct fasync_struct ** fapp)690 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
691 {
692 if (!on)
693 return fasync_remove_entry(filp, fapp);
694 return fasync_add_entry(fd, filp, fapp);
695 }
696
697 EXPORT_SYMBOL(fasync_helper);
698
699 /*
700 * rcu_read_lock() is held
701 */
kill_fasync_rcu(struct fasync_struct * fa,int sig,int band)702 static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
703 {
704 while (fa) {
705 struct fown_struct *fown;
706 unsigned long flags;
707
708 if (fa->magic != FASYNC_MAGIC) {
709 printk(KERN_ERR "kill_fasync: bad magic number in "
710 "fasync_struct!\n");
711 return;
712 }
713 spin_lock_irqsave(&fa->fa_lock, flags);
714 if (fa->fa_file) {
715 fown = &fa->fa_file->f_owner;
716 /* Don't send SIGURG to processes which have not set a
717 queued signum: SIGURG has its own default signalling
718 mechanism. */
719 if (!(sig == SIGURG && fown->signum == 0))
720 send_sigio(fown, fa->fa_fd, band);
721 }
722 spin_unlock_irqrestore(&fa->fa_lock, flags);
723 fa = rcu_dereference(fa->fa_next);
724 }
725 }
726
kill_fasync(struct fasync_struct ** fp,int sig,int band)727 void kill_fasync(struct fasync_struct **fp, int sig, int band)
728 {
729 /* First a quick test without locking: usually
730 * the list is empty.
731 */
732 if (*fp) {
733 rcu_read_lock();
734 kill_fasync_rcu(rcu_dereference(*fp), sig, band);
735 rcu_read_unlock();
736 }
737 }
738 EXPORT_SYMBOL(kill_fasync);
739
fcntl_init(void)740 static int __init fcntl_init(void)
741 {
742 /*
743 * Please add new bits here to ensure allocation uniqueness.
744 * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
745 * is defined as O_NONBLOCK on some platforms and not on others.
746 */
747 BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
748 HWEIGHT32(
749 (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
750 __FMODE_EXEC | __FMODE_NONOTIFY));
751
752 fasync_cache = kmem_cache_create("fasync_cache",
753 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
754 return 0;
755 }
756
757 module_init(fcntl_init)
758